This invention relates generally to a new and useful improvement in meat separating machines of the type wherein a conveying screw or auger rotates within a foraminous cylinder or sleeve-like screen so as to separate meat from an infeed material which has an appreciable content of sinew-like material and bone particles. In particular, this invention relates to improvements in the foraminous screens or cylinders utilized in such meat separating machines.
Rotary screw-type deboners or meat separating machines of the type in which a foraminous cylinder or sleeve-like screen and conveying auger or screw form important components are disclosed in a number of U.S. Pat. Nos. including: RE 32,531 to Beck et al. dated Oct. 27, 1987; RE 31,631 to McFarland dated Jul. 17, 1984; 4,303,206 to Prince et al. dated Dec. 1, 1981; 4,546,927 to Bloome and Shaw dated Oct. 15, 1985 and 4,824,027 to Shaw and Brooker dated Apr. 25, 1989. The disclosures of Beck et al. RE 32,531, Bloome and Shaw 4,546,927 and Shaw and Brooker 4,824,027, all assigned to The Kartridg Pak Co. of Davenport, Iowa, are incorporated by reference herein. In meat separating machines of the foregoing type an infeed containing appreciable contents of sinew-like material and bone particles is subjected to continuous axial compression of the meat-sinew-bone mass with resultant extrusion of liquid meat through the holes or foramina in the cylinder on screen surrounding the compression conveying screw or auger.
In accordance with this invention, it has been ascertained that the efficiency of operation of such a screw-type deboner or meat separating machine depends upon the relative ability of the screw or auger to generate high compression inside the screen or cylinder by minimizing circumferential slip of the meat-sinew-bone mass with respect to the stationary screen and maximizing slip with respect to the flights on the rotating screw or auger. The degree to which undesirable circumferential slip occurs is believed to reduce the efficiency of the separating process resulting in additional passes of the meat-sinew-bone mass over the screen orifices, thereby frictionally increasing the temperature of the extruded meat product and the amount of bone sheared off by the edges of the screen orifices which passes out as fine bone particles with the meat product.
According to the present invention, the screen anti-rotational gripping action on the meat-sinew-bone mass is materially increased by the design of the screen hole drilling configuration or pattern which eliminates undrilled circumferential areas or bands in the screen drilled areas and by increasing the number of holes or orifices for a given size orifice or hole. The anti-rotational gripping tendency is produced and enhanced by the extrusion of meat fibers into the screening holes or orifices. These fibers tend to plug the screen holes or orifices and are cut off by either the edge of the compression screw flights, in the case of meat separating machines wherein the augers rotate at relatively low revolutions per minute (e.g. under about 200 rpm), or by the relatively high speed motion of the bone particles or fragments in the case of high auger rpm machines (e.g. 900 rpm and above).
Previous screen or foraminous cylinder designs were based upon drilling patterns of circumferentially extending rows of holes which resulted in intervening undrilled parallel circumferetial bands extending at 90.degree. to the longitudinal axis of a cylinder. It is now believed that these undrilled band areas resulted in a reduction of engagement of the meat fibers per unit area and a correspondingly lower anti-rotational frictional grip on the meat-sinew-bone mass.
The drilled hole pattern in accordance with the present invention provides an optimum hole configuration which eliminates the prior undrilled circumferential bands while increasing the number of gripping holes or orifices. The result is that in a typical operation, the meat product temperature rise is substantially reduced (i.e. typically by 15.degree.-20.degree. F.) with a concurrent increase in throughput for a given bone discharge orifice setting (e.g. 30 to 40% increases in throughput).
The object of the invention, generally stated, is the provision of new and improved foraminous cylinders or sleeve-like screens for use in rotary screw-type deboners Which in the operation of such meat separating machines result in substantial reductions in the temperature rise of the separated or extruded meat while at the same time substantially increasing the throughput capacity of the machines.
An important object of the invention is to be able to achieve such significant reductions in temperature and concurrent increases in throughput by utilizing patterns for the foramina or holes in the walls of the screens or cylinders which eliminate the prior undrilled circumferential bands and which greatly increase the number or concentration or holes or orifices.